Prof. Sei Suzuki (Saitama Medical University)
"Slow quantum quench near a discontinuity critical point"
When a macroscopic system is driven from a disordered phase to an ordered phase by lowering the temperature, one encounters spontaneous generation of topological defects, namely, vortices, kinks, and domain walls. The mechanism of this phenomenon is explained by the Kibble-Zurek mechanism. Following the recent progress in the cold-atom experiments, the quenching dynamics of a closed quantum system near a quantum phase transition draws a lot of attention. So far, a number of studies have revealed scaling properties of the defect density and the residual energy after a quantum quench across a quantum critical point. However, most of them are associated with continuous transitions, and the discontinuous (first-order) transition has not been received much attention. In the present seminar, we discuss a discontinuous transition, focusing on a discontinuity critical point (DCP) in particular. After introducing the notion of a quantum version of a DCP, we provide universal scaling relations associated with a quantum DCP separating two gapped phases, two gapless phases, or a gapped and gapless phases. We then study quantum quench of a quantum DCP and propose scaling laws for the density of defects and the residual energy after a quench. These are verified with the spin-1/2 XXZ chain.